This invention relates to viewing systems, and in particular to an improved viewing system for producing a simulation of depth in substantially two-dimensional visual images such as television images. The invention also relates to improvements in viewing systems for improving clarity and color rendition in such two-dimensional images.
Conventional systems for producing the appearance of depth in two-dimensional images incorporate depth information in the image itself, and provide special viewing means for utilizing the depth information. For example, in the now obsolete "3-D" motion pictures, the image displayed on the motion picture screen was actually two superimposed images which were separated by means of polarizers or colored filters. The polarizers or colored filters were incorporated in special glasses or viewers provided to the theater patron so that one eye of the patron would perceive one of the two images, and the other eye would perceive the other of the two images.
Various unconventional attempts have been made in the past to produce the simulation of depth in the viewing of two-dimensional images containing no special depth information. For example, the image on a television screen, or the image of a conventional motion picture on a motion picture screen, contains no special depth information, and can be viewed in the conventional manner without giving the impression of depth.
One such attempt at depth simulation was described in U.S. Pat. No. 4,049,339, issued Sept. 20, 1977 to Antoine Ledan. Ledan described a pair of eyeglasses for movie viewing which are designed to produce a simulated three-dimensional effect. The eyeglasses have flat, triangular-shaped lenses in an opaque frame. These lenses are arranged so that the left edge of the image on the movie screen is obscured from view through the left eye, and so that the right edge of the image is obscured from view through the right eye. The eyeglasses described by Ledan produce the sensation of depth by the so-called "window effect", i.e. by preventing the observer from determining the distance between himself and the movie screen. The effect described in the Ledan patent is somewhat similar to the effect utilized to simulate depth in wide-screen and curved-screen movie systems. The purpose of the wide screen or the curved screen is to fill the observer's field of view, preventing him from seeing the edges of the screen and thereby determining the distance between his eyes and the screen.
Another approach to producing illusions of depth is described by Hugh M. Stevenson in his U.S. Pat. No. 2,922,998, dated Jan. 26, 1960. Stevenson describes a television having, in front of the picture area, a sheet of transparent material with opaque or translucent vertical lines. According to Stevenson, the illusion of depth is due to the slightly different picture presentation for each eye combined with the placement of the substantially vertical parallel lines in front of and spaced apart from the plane of the picture presentation.
Another system for depth simulation was described by H. M. Muncheryan in his U.S. Pat. No. 2,986,969, dated June 6, 1961. Muncheryan described a binocular device having a pair of relatively rotatable polarizers in each eyepiece. Depth simulation was achieved by rotating the plane of polarization of one polarizing lens with respect to the other in one eyepiece until objects viewed have obtained apparent curvatures and depths. This effect is said to be more prominent in the angular range of 30 to 50 degrees between the polarization axes of the two polarizing elements. After the polarizers in one eyepiece are adjusted, the polarizing lens of the other eyepiece is rotated until the transmitted light intensity through that eyepiece is comfortable to the eye.
Another optical aid for simulating depth in two-dimensional images such as screen projections, drawings and photographs, was described by A. Ames, Jr. in U.S. Pat. No. 1,636,450, dated July 19, 1927. Ames used a pair of eyeglasses having a system of prisms and lenses which eliminated actual perceptive sensations. The system blurred the image seen by one eye, preferably by means of a cylindrical lens which blurs only vertical lines, leaving horizontal lines sharp. The theory of operation, as explained by Ames, is that the system of prisms and lenses causes the position of the picture in space to be indeterminate. The system of prisms and lenses causes both eyes to be relaxed in convergence and in their accommodations. The eyes are caused to have differently relaxed accommodations, which prevent any sensory ascertainment of distances by accommodative stress. The result is to free the observer from any compulsory suggestion arising from actual perceptive sensations, and from any compelling belief that the arrangement of line and light and shade before the viewer lie in any one plane. The reaction in the observer is that the picture objects appear in near and far relation suggested by their sizes, shadows and perspective.
F. Pole, in U.S. Pat. No. 2,884,833, dated May 5, 1959, describes a three-dimensional effect produced by means of a transparent, curved lenticular screen, having an array of individual lenses, which are preferably so small that they cannot be discerned by the normal eye when viewed from the normal viewing distance.
Nawokich Tanaka in U.S. Pat. Nos. 2,374,566, dated Apr. 24, 1945, 2,888,855, dated June 2, 1959 and 3,053,135, dated Sept. 11, 1962, describes several versions of a system for simulating three-dimensional viewing in which, by means of a special reflector or lens system, secondary images are produced which are said to give rise to a three-dimensional effect.
In French Pat. No. 1,101,550, granted Apr. 20, 1955, Gilbert-Jacques Robin describes the creation of stereoscopic effects by using a transparent plate having alternately interpositioned convergent and divergent cylindrical lenses. The plate has a large number of lenses, typically one lens for each millimeter of plate width. The number of lenses is related to the locations of the image plane, the plate and the observer so that, for any given very small area on the image plane, one eye will see it reduced, and the other eye will see it enlarged.
In all of the foregoing viewing systems of the prior art, a simulated three-dimensional effect is achieved at the expense of image quality. That is, each system of the prior art either partially obscures the image or produces a blurring of visual information. In the former case there is at least a loss of light from the picture, and the loss of light may be accompanied by a loss of picture information. In the latter case, blurring of visual information has a tendency to cause eyestrain, and to make viewing for extended periods of time somewhat unpleasant. Nevertheless, apparently obscuration and/or blurring have been considered essential heretofore in the production of three-dimensional effects from conventional two-dimensional images.